This relates generally to analog to digital converters.
Sigma delta converters are noise shaping, oversampled data converters that realize processing gains in effective dynamic range by accepting increased conversion time in order to realize higher conversion accuracy. Accuracy is achieved by employing an oversample rate that is greater than the Nyquist sampling rate. Furthermore, multilevel feedback gains may be incorporated to further extend dynamic range.
The sigma delta analog to digital converter measures at low resolution, but high rate. In order to form a continuous time analog to digital converter, the sample may be taken inside the feedback loop instead of at the input. Nonetheless, the system may become very sensitive to the delay of the loop.
Thus, delay compensation systems are useful. More particularly, a compensation loop is needed for the delay in the feedback gain g. That compensation may be achieved by compensating the forward gain h.
By making the phase of the g term “early” and the phase of the h term “late,” a phase lead network can be established.